GB1152366A - Improvements in or relating to Electrical Arc Furnaces - Google Patents

Abstract

1,152,366. Electric arc furnaces. CENTRAL ELECTRICITY GENERATING BOARD. 9 Feb., 1967 [22 Nov., 1965], No. 49529/65. Heading H5H. An arc furnace with A.C. supply means has means for separately supplying D.C. in parallel with the A.C. supply means to stabilize the arc. The furnace has three electrodes 2 supplied by the secondary windings of a 3-phase transformer 3a whose primary windings are supplied through connections 4 from bus-bar 5 supplied from a 3-phase source 6 which also feeds a load 7. The auxiliary D.C. supply is obtained from a bridge 9, of grid-controlled valves or diodes supplied from a 3-phase transformer 8 whose primary windings are connected to the bus-bars 5, and the D.C. output is superimposed on the A.C. output of transformer 3a by feeding it through an interconnected star/star transformer 10a, or a group of three shunt reactors 10b, and returning it along a line 13a or 13b from an additional electrode. A smoothing reactor 11 is provided in the D.C. circuit. Transformers 3a and 10a may be replaced by a single transformer 3b, Fig. 3 (not shown). Another arrangement provides for a supply from two phases only through a transformer 3c, Fig. 4 (not shown).